[adolph]

120k years ago in context:

  * 170,000 years ago: humans are wearing clothing by this date.
  * 125,000 years ago: the peak of the Eemian interglacial period.
  * ~120,000 years ago: possibly the earliest evidence of use of symbols etched onto bone
  * 75,000 years ago: Toba Volcano supereruption that may have contributed to human populations being lowered to about 15,000 people

https://en.wikipedia.org/wiki/Timeline_of_prehistory

The Eemian climate is believed to have been warmer than the current Holocene. Changes in the Earth's orbital parameters from today (greater obliquity and eccentricity, and perihelion), known as Milankovitch cycles, probably led to greater seasonal temperature variations in the Northern Hemisphere. During the northern summer, temperatures in the Arctic region were about 2-4 °C higher than in 2011.

The hippopotamus was distributed as far north as the rivers Rhine and Thames. . . . The prairie-forest boundary in the Great Plains of the United States lay further west near Lubbock, Texas, whereas the current boundary is near Dallas. . . . Sea level at peak was probably 6 to 9 metres (20 to 30 feet) higher than today . . . .

https://en.wikipedia.org/wiki/Eemian

[angiosperm]

There is definite evidence of hominins in North America 130,000 years ago (search "Cerutti mastodon"). Nobody knows if they were H. erectus, Neanderthal, Denisovan, modern humans, or "other", but with an interglacial at 125,000 years ago, it is not hard to see how they could have got here.

[biztos]

Wikipedia suggests this is not definitive, and maybe not even evidence:

https://en.wikipedia.org/wiki/Cerutti_Mastodon_site#Criticis...

This article is much more sympathetic (and also a fun read):

https://www.latimes.com/local/california/la-me-cerutti-masto...

I’m no expert but it seems like this is still a controversial idea.

[angiosperm]

Wikipedia over-represents the opinions of retired professors. As Max Planck wrote, "Science advances one funeral at a time".

The usual shallow, reflexive objection is that the bones must have been broken and carefully re-arranged via being run over by construction equipment. This absurd suggestion has been very thoroughly demolished without assistance from construction equipment. It is hard for dump truck tires to produce green-stick fractures in 130,000-year-old bone, or to put bone fragments into the pores of stones and then move them yards away, all while underground.

[orangepurple]

This raises a very critical point. Nuclear is the only dependable energy source. Fossil fuels will run out or go out of favor. Solar and wind on the other hand will become victims of the next major volcanic eruption as ash destroys them or renders them ineffective.

[XorNot]

Deep drilling based geothermal can fill this role too though - and does have the substantial benefit over nuclear that it leaves no surface-supply chains for resources (uranium).

Given that we're so close to being able to do it, we honestly need a Manhattan project initiative to push it through to reality (with the outcome being the machine and process to do the drilling).

[dredmorbius]

An eruption significant enough to impact solar and wind generation globally will also affect other critical requirements of humanity, and the Earth's ecosystem, globally.

Which is to say: You Will Be Having Bigger Problems.

Recovery from regional meterological catastrophes is well within human capabilities.

[zosima]

Bigger problems than no power in the worst year imaginable. Give me a break.

[Server6]

Yeah. Crop failures and famine. Way bigger problem.

[zosima]

Availability of energy can mitigate crop failure and lack of energy also leads to crop failure.

How can people not generally understand the connection?

[dredmorbius]

And depending on the eruption, for anywhere from years to centuries or longer.

[sanderjd]

Yes, no agriculture is an even bigger problem than no power.

[zosima]

You don't think modern agriculture and energy are intimately related?

I'm honestly a bit shocked.

[sanderjd]

I do think they are, but it's also (obviously) the case that if an eruption blotted out the sun and disrupted wind currents, having the ability to keep generating power would not help much because the plants and animals we eat would all die.

And what's with the weird tone? It's a super banal point that our food requires sun. I highly doubt you're "shocked" by it.

[orangepurple]

You are thinking too far ahead. There is a real risk of persistent cloud cover and ash in many places without total crop failure.

[ricardobeat]

Nuclear facilities seem pretty fragile / demanding, I doubt one would survive any kind of apocalyptic event. The infrastructure supporting it will be gone.

[orangepurple]

Nuclear facilities can probably continue to operate amid persistent cloud cover and ash. Wind turbines and solar can not. Agriculture would have to shift artificially lit greenhouses.

[fullstackchris]

isnt that the case with any advanced technology? (including wind and solar)

[dredmorbius]

Yes.

Though as a corollary, such an event would be civilisation-ending in any regard.

It's also ... highly rare. Somewhere in the 1 in a million to 100 million year range, which is to say, not only longer than the planning horizon of most human institutions, but well outside the existence of the human species for the most part.

It's also well beyond the available supply of terrestrially-minable uranium,[1] and possibly of ocean-extracted uranium,[2] and thorium[3]. Breeders might be another option, though I've seen no substantive estimates of total fuel availability for that case either.[4]

But as an argument favouring nuclear over other energy options ... this is pretty silly, really.

About the only viable defence against such a risk would be, and I say this as someone who's markedly pessimistic on space colonisation, independent and self-sufficient habitations off-Earth: YACP.[5]

________________________________

Notes:

1. If we relied on naturally-occurring terrestrially-mined uranium for all present human energy consumption ... supplies would last fewer than two decades. This is seldom mentioned by nuclear advocates.

2. This offers a potentially much larger supply, as uranium is present as a solute in seawater, but viable industrial-scale extraction is unproven and would require filtering vast quantities of seawater.

3. Thorium is reasonably abundant, though I'm not quite sure how abundant. Thorium-based reactors are not much used, and the concept of molten-salt reactors (MSR) which gained some popularity in the past decade ... faces some very significant engineering hurdles. Managing high-temperature highly-corrosive radioactive salts is ... challenging.

4. Breeders produce plutonium. And now you have two, or more, problems.

5. Yet Another Challenging Proposition.

[wheelerof4te]

"75,000 years ago: Toba Volcano supereruption that may have contributed to human populations being lowered to about 15,000 people."

The key question is: How much CO2 did that super-eruption emit into the atmosphere?

In our hurry to attribute climate change to our meager impact on this planet, we tend to forget what horrors an eruption of this magnitude can cause. And who knows how many of them happened during the past millennia.

[pmayrgundter]

The figure I've found is 2800 km^3 of approximately granite, which at 2.7 tonnes per cubic meter gives about a billion gigatons ejecta.

I've never found a CO2 estimate, but did find that it's a significant amount of that mass, as is SO2.

It wasn't worth me doing more of a sketch since it's not clear how to model the effects of such a massive system.

I was struck tho, that the magnitude of this and a few other events in the not too distant past, are vastly larger than even all put nuclear war

It's not clear to me that our CO2 emissions are very significant in comparison

[dredmorbius]

Wikipedia cites a range of 2,000 -- 13,000 km^3.

<https://en.wikipedia.org/wiki/List_of_largest_volcanic_erupt...>

As for the gaseous component of ejecta:

Water vapour is consistently the most abundant volcanic gas, normally comprising more than 60% of total emissions. Carbon dioxide typically accounts for 10 to 40% of emissions.

<https://en.wikipedia.org/wiki/Volcanic_gas>

Citing: H. Sigurdsson et al. (2000) Encyclopedia of Volcanoes, San Diego, Academic Press.

(Late edit: though I note that this seems to discuss percentages of gaseous emissions, not total ejecta. Anyone have a better source here?)

One of the largest volcanic events I'm aware of is the Siberian Traps eruption, about 250 mya, with a volume of about 4 million km^3, another three orders of magnitude greater than Tomba.

This has been linked to the Permian–Triassic mass extinction event, with the mechanism being release of methane clathrates and/or stimulating growth of a microbe which released vast quantities of methane into the atmosphere, killing ~81% of all extant marine species and 70% of terrestrial vertebrate species.

<https://en.wikipedia.org/wiki/Siberian_Traps>

"The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to the ocean-atmosphere system during this period."

-- Wikipedia, citing Wu, Yuyang; Chu, Daoliang; Tong, Jinnan; Song, Haijun; Dal Corso, Jacopo; Wignall, Paul B.; Song, Huyue; Du, Yong; Cui, Ying (9 April 2021). "Six-fold increase of atmospheric pCO2 during the Permian–Triassic mass extinction". Nature Communications. 12 (1): 2137. Bibcode:2021NatCo..12.2137W. doi:10.1038/s41467-021-22298-7.

<https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extin...>

[pmayrgundter]

Good finds. Thanks!

Yeah, it's the comparison between DRE and Gas ejecta that got me bogged down before.

Having now given up, I asked ChatG4. It says "the mass ratio between DRE and gaseous emissions might be on the order of 20:1 to 100:1", no citations ofc.

So, just as a strawman and using your 10-40%, on the low end .01.1 = 0.001, high end .05.4 = 0.02. So .1%-2% of ejecta by mass is CO2 emissions. Hah :)

Using my orig figure for Toba of a billion gigatons of ejecta, of which roughly a million gigatons would be CO2. Correct math?

Human GHG emissions are ~50 Gt/year.

[dredmorbius]

DRE == dense rock equivalent:

<https://en.wikipedia.org/wiki/Dense-rock_equivalent>

[pmayrgundter]

Math glitch. It was a million gigatons DRE, so 1000 Gt CO2

[FireBeyond]

I think people struggle with the magnitude.

Mt St Helens, for example. Not the largest eruption.

But a landslide of approximately 2.5km^3 (over 3 billion cubic yards).

Okay, some say, so that is a lot of earth...

and then you learn that the landslide was moving at speeds of up to 160mph.

That's a LOT of energy.

[wheelerof4te]

It sure is. And we've yet to survive our modern-day supervulcano eruption.

[groby_b]

"And who knows how many of them happened during the past millennia.

Geologists. And the answer is "none" for the past 25 or so millenia, and "one" since Toba.

Also, unless you've had supervolcanoes go off in your bedroom and didn't tell anybody, the evidence for human impact is exceedingly clear.

[wheelerof4te]

"Geologists."

Geologists might know, same as astronomers might know what Black Holes and Pulsars really are.

On the other hand, it is a geologist's call to search for answers and for truth. Saying that they truly know is the same as saying nothing.

[mschuster91]

> And who knows how many of them happened during the past millennia.

We at least have a significantly large list of what we know [1] - that's part of the purpose of core drilling, the ash deposits worldwide can be linked together to estimate where ash traveled to. Also, craters and their surrounding can be drilled into to determine eruption events.

[1] https://en.wikipedia.org/wiki/List_of_large_volcanic_eruptio...

[pmayrgundter]

Here's a study:

The size and frequency of the largest explosive eruptions on Earth, Mason 2004

https://www.researchgate.net/publication/227000709_The_size_...

[sci_prog]

Not even close to what we as humans emit. The rate of the global annual natural CO2 emissions are 1-2 orders of magnitude slower than anthropogenic emissions.

[saltymug76]

If you're trying to minimize human caused warming with the rare eruption of super volcanoes, it's pretty weak.

[wheelerof4te]

Where is the evidence of human effect on the climate change? There is a huge effect on pollution, but hardly any on the global climate.

[saltymug76]

Considering the rapid rise in temperature on a relatively miniscule geological timescale, I'd be more interested to see evidence that it's not a manmade phenomenon.

[wheelerof4te]

There's a huge increase of human population living in very large cities, when compared to 100 years ago. Especially in China and India.

Of course the people will feel the local rise of temperature in asphalt-ridden and industry-polluted streets. It's logical.

This does not mean that global climate has changed.

[staunton]

Volcanoes aren't about the CO2, they're about the ash which blocks out the sun and makes it colder.